(Reuters) -Boeing sent a contract offer on Tuesday to union members who assemble its fighter jets in the St. Louis area.

The company's proposal includes a 20% general wage increase over four years and a $5,000 ratification bonus, as well as more vacation time and sick leave.

Local union leaders are recommending that the more than 3,200 members of the International Association of Machinists and Aerospace Workers District 837 approve the contract when they vote on Sunday, the day it expires.

Boeing's defense division is expanding manufacturing facilities in the St. Louis area for the new U.S. Air Force fighter, the F-47, after it won the contract earlier this year.

The company is expected to expand its workforce in the coming years, as well.